6 replies to this topic

[Elias]

Hi, this is my first post on odforce!

I've been playing around with particles for a few days now and I can't get the hang of the Creep operator. My goal is to distribute particles on a nurbs surface, to accomplish this I emit a 100 particles from a sphere at frame 1. Then I add a interact node to have them repel each other, and finally I add a creep operator to have them constrained to the surface. However, all my particles seem to move to the position of the 100:th particle (id 99). This seems very strange to me, should the creep operator be used in a different way?

When I have solved that part I want to stamp geometry onto the particles, using the particle scale to add some variance in size. I will also use add some randomized point jitter to my instanced polygon cubes. This part I think I know how to do, but extracting the particle scale is something I have never done before.

Is my approach valid or should I try to go a different route? I've thought about the scatter SOP but I figured I would need particles to avoid intersecting geometries.

[digitallysane]

Take a look at the examples in the Creep POP help page, those might help.

http://localhost:48626/nodes/pop/creep

http://www.sidefx.co...nodes/pop/creep

[Elias]

I had a good look at the example files, it was quite helpful. However, they all seem to use to UV's to animate along the surface. In my case I wan't my particles to interact with each other based on their proximity. This might have been more difficult than I originally thought. I think that the interact operator may still be the way to go, possibly using it to spread the particles out, check for the closest point on the surface and add an acceleration in the direction of that point. I'm a novice and I don't know how to do this in Houdini.

[3dbeing]

It's always easier to explain solutions when the problem is presented in .hip format.

I, personally, don't like the interact pop.  That being said, I may not understand properly how to use it.

But here's how to use the creep sop...
creep

[Elias]

Okay here is a simple scene describing what I'm trying to achieve.

Attached Files

•  surfaceParticles.hip   76.84K   36 downloads

[bloomendale]

Creep POP is a bit useless thing imo.
I'd suggest you to sample your to sample your geo as sdf volume + find the gradient of that volume in vop pop and use these vectors to constrain your particles to surface.

[Elias]

bloomendale, on 05 July 2012 - 01:21 PM, said:

Creep POP is a bit useless thing imo.
I'd suggest you to sample your to sample your geo as sdf volume + find the gradient of that volume in vop pop and use these vectors to constrain your particles to surface.

That sounds like a plan. I'm clueless of how to do it though, would you mind explaining it a little bit further?